Cell membranes are soft materials that play critical roles in physiological processes both by acting as selectively permeable barriers and by providing a two-dimensional, liquid crystalline bilayer in which transmembrane proteins are anchored. The membrane is involved in physiological processes ranging from homeostasis to vesicle trafficking and many other forms of cellular signaling. For these reasons, methods to quantify physical properties of membranes provide direct insight into how their structures impact their functions.
Further, there is increasing evidence that biomacromolecules,1-3 cell-penetrating peptides4,5 and nanoparticles,6-8 and other small molecules such as anesthetics or drugs9-12 affect the packing and conformations of lipids in the membrane. For example, the bulk hydrophobic region of cholesterol is known to affect the structural order and fluidity of phospholipid bilayers by interdigitating between the acyl chains of neighboring lipids.13-17 And because the interactions between lipid bilayers and cholesterol, transmembrane proteins, and membrane active pharmaceuticals can alter the tension of the membrane, methods for quantifying membrane tension can be applied to study the uptake and accumulation of a variety of important species into lipid bilayers.1 
Conditions for studying biological membranes in vivo can be limited by the requirement to keep cells healthy. Thus, artificially prepared models of biological membranes (i.e., biomimetic membranes) are often used to study biological membranes in vitro. However, efforts to determine multiple different physical properties of the same artificial membrane can be difficult due to the need to use different apparatus.
As a consequence, compositions, systems, and methods for determining multiple physical properties of model biological membranes with accuracy and sensitivity are needed. In particular, methods and apparatus to determine multiple properties using the same apparatus or general experimental conditions are needed to make the study of biomimetic membranes more efficient, both with regard to time and expense.